Babymetal’s fame surprises even them. The trio, a group of Japanese teens, became a viral sensation in 2014 with their heavily choreographed video for “Gimme Chocolate!!” – a song that showcased their glossy fusion of pop music and heavy metal. Since then, on various international tour dates including a run supporting Lady Gaga, they’ve met some of their idols (Ariana Grande, Marilyn Manson) and have been bowled over by people’s responses.

“In the past two years, we’ve performed in many different places,” singer Su-metal told Rolling Stone during a short visit to New York. “We’ve noticed that even though we sing in Japanese, our fans study Japanese and sing along with us, and that people who like J-pop and people who like metal both enjoy our music just the same.”

The group tested its fan base further earlier this month, when it issued a follow-up to its self-titled debut: Metal Resistance. The lead single, “Karate,” shows the group’s affection for its country’s martial arts, and serves a higher, more personal purpose for the young women. “The theme of ‘Karate’ is about fighting yourself to break down barriers and move forward,” Su-metal says. The reaction has been positive. Its video has attracted more than 8 million views since they released it last month, and the LP debuted at Number 39 on the Billboard 200 and Number Two on its Hard Rock chart.

While Babymetal were in New York — the group will tour the States this summer with dates in May and July – they told Rolling Stone about the “Karate” video and offered up a suggestion of some inspiring source material: The Karate Kid and YouTube. “Something we thought was really cool was seeing this [YouTube] video of a nine- or 10-year-old girl doing karate,” Su-metal says. “It was so cool. She was much smaller than us, but her moves were huge, and we wanted to do karate just like that.”